U.S. patent number 5,846,657 [Application Number 08/888,488] was granted by the patent office on 1998-12-08 for liquid crystal displays containing spacers and methods for producing the spacer.
This patent grant is currently assigned to Rohm and Haas Company. Invention is credited to Jiun-Chen Wu.
United States Patent |
5,846,657 |
Wu |
December 8, 1998 |
Liquid crystal displays containing spacers and methods for
producing the spacer
Abstract
Methods for preparing uniformly sized polymer particles
comprised of multi-functional monomers such as poly(1,4-butanediol
diacrylate) and poly(1,6-hexanediol diacrylate) are disclosed. The
particles are of a size, uniformity, and contan physical
characteristics that make them ideally suitable for use as spacers
in liquid crystal display devices.
Inventors: |
Wu; Jiun-Chen (Robbinsville,
NJ) |
Assignee: |
Rohm and Haas Company
(Philadelphia, PA)
|
Family
ID: |
21811017 |
Appl.
No.: |
08/888,488 |
Filed: |
July 7, 1997 |
Current U.S.
Class: |
428/402;
526/323.2 |
Current CPC
Class: |
C08F
22/1006 (20200201); G02F 1/13392 (20130101); C08F
291/00 (20130101); C08F 265/06 (20130101); C08F
265/04 (20130101); C08F 20/18 (20130101); C08F
257/02 (20130101); C08F 291/00 (20130101); C08F
2/22 (20130101); Y10T 428/2982 (20150115) |
Current International
Class: |
C08F
291/00 (20060101); C08F 265/04 (20060101); C08F
257/02 (20060101); C08F 20/00 (20060101); C08F
20/18 (20060101); C08F 22/00 (20060101); C08F
22/10 (20060101); C08F 265/06 (20060101); C08F
265/00 (20060101); C08F 257/00 (20060101); G02F
1/13 (20060101); G02F 1/1339 (20060101); B32B
005/16 (); C08F 020/10 () |
Field of
Search: |
;526/323.2 ;428/402
;359/81 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
63-79065 |
|
Apr 1988 |
|
JP |
|
WO 92/06402 |
|
Apr 1992 |
|
WO |
|
Other References
"Preparation of Nonspherical, Monodisperse Polymer Particles and
Their Self-Organization", A. T. Skjeltorp, J. Ugelstad, T.
Ellingsen, Journal of Colloid and Interface Science, vol. 113, No.
2, pp. 577-582, Oct. 1986. .
"Advances in Colloid and Interface Science", J. Ugelstad. P. C.
Mark, 13, 101-140 (1980). .
"New Developments in Production and Application of Monosized
Polymer Particles". J. Ugelstad, T. Ellingsen, A. Berge, Polym
Matur Sci Eng, 54, pp. 521-525, 1986..
|
Primary Examiner: Lipman; Bernard
Assistant Examiner: Sarofin; N.
Attorney, Agent or Firm: Lemanowicz; John Frickey; Darryl
Gironda; Kevin
Claims
What is claimed is:
1. A plurality of spacers comprising crosslinked particles
comprised of homopolymers or copolymers of multi-functional
acrylate monomer selected from 1,4-butanediol diacrylate and
1,6-hexanediol diacrylate as polymerized units; wherein said
cross-linked particles have a particle size of about 1 to about 15
microns with a standard deviation in particle size of less than 3%
of the mean diameter, a compression value of greater than 150
kilograms per square millimeter, and a recovery factor of greater
than 45 percents the standard deviation in particle size is
invariant with particle size diameter and a narrow particle size
distribution is achieved without classification processes.
2. The spacer of claim 1 wherein the coefficient of thermal
expansion is from 100.times.10.sup.-6 /.degree. C. to
125.times.10.sup.-6 /.degree. C.
3. The spacer of claim 1 wherein the spacer contains adhesive
properties.
4. The spacer of claim 1 wherein the spacer is coated with a
conductive coating.
5. The spacer of claim 1 wherein the spacer is colored.
6. The spacer of claim 3 wherein the adhesive property is derived
from a combination of reactive coupling and thermoplastic
resins.
7. The spacer of claim 6 wherein the reactive coupling agent
contains free radicals generated from the absorption UV
radiation.
8. The spacer of claim 7 wherein the reactive coupling agent is
2-hydroxy-(3-methacryloxy)-propyl-1-(2-benzoyl)benzoate.
9. The spacer of claim 6 wherein the thermoplastic resin is
tert-butyl methacrylate.
10. The spacer of claim 4 wherein the conductive coating is nickel
or gold.
Description
This is a nonprovisional application of prior pending provisional
application Ser. No. 60/022,707 filed Jul. 25, 1996.
BACKGROUND OF THE INVENTION
This invention relates to polymeric compositions made from
multi-functional monomers, especially multi-functional acrylate
monomers such as 1,4-butanediol diacrylate and/or 1,6-hexanediol
diacrylate, a process to make the polymeric compositions, and the
use of the polymeric compositions as spacers in liquid crystal
displays. Other embodiments of the invention relate to providing
the spacer particles with adhesive properties or conductive
properties or further coloring the spacer particles.
It is very important to have precise control of the thickness of
the liquid-crystal layer in liquid-crystal-based displays. The
liquid-crystal layer acts as an electro-optic light valve that
works in conjunction with polarizers to modulate the transmission
of light through a display between two states: one of off, where
the liquid crystals block substantially all light; and one of on,
where the liquid crystals allow transmission of light.
Irregularities in the thickness of the liquid-crystal layer, also
known as the cell gap, result in uneven display performance
affecting such properties as contrast, transmittance, and the
response time of the liquid-crystal layer to an electric
signal.
Liquid crystal displays have a structure such that two substrates,
generally glass or plastic sheets, are disposed opposite to each
other through optionally a color filter on the inside surface of
the top substrate (top is the side toward the viewer), an alignment
layer, an electrode layer, a spacer particle, and a liquid crystal
layer. A purpose of the spacer particle is to control the thickness
of the liquid crystal layer and another purpose is to provide a
uniform thickness of the liquid crystal layer over the entire
active area of the display. Other means for controlling the cell
gap include the flatness of the substrate material, the flatness of
the layers between the substrates, the number of spacer particles
in any given area, and the spatial distribution of spacer particles
with respect to one another.
Particles generally suitable for use as spacers in liquid crystal
displays are chosen from among: glass; oxides of silica, alumina or
other ceramics; and plastics. The shape of particles generally
suitable for use as spacers in liquid crystal displays are chosen
from among: cylindrical rods having aspect ratios from about 1:2 to
greater than 1:10; and spherical balls. The choice of spacer
particles is largely dictated by the characteristics of the spacer
particles that include but are not limited to: uniformity of the
particle diameter, amount of impurities that may leach into the
liquid crystal layer, compatibility with the liquid crystal layer,
hardness, compressibility, coefficient of thermal expansion,
elastic modulus, refractive index, thermal stability, and
dielectric constant.
The importance of spacer particles in maintaining the cell gap has
been described herein. In addition, spacer particles are very
important in establishing the correct cell gap during the assembly
of liquid crystal displays. The liquid-crystal display assembly
process generally requires the following steps: a) spacer particles
are deposited in a pre-determined concentration onto one sheet of
glass or plastic substrate, b) a sealant is applied along the edge
of the same substrate in a fashion similar to a picture frame
leaving a small gap that will later be used for filling with the
liquid crystal material, c) a second sheet of glass or plastic
substrate is placed over the first substrate containing the spacer
particles and the adhesive, d) the two substrates are pressed
together at an elevated temperature to cure the adhesive and
therefore sealing the substrates together. The properties of the
spacer particles must be such that the particles do not degrade
during the application of heat and pressure in the sealing process;
the spacer particles must have sufficient thermal stability to
withstand heating and also good compression strength so as to not
break or fracture under load.
Plastic spacers will deform in the edge-sealing process described
above. The extent of deformation can vary significantly, and is a
function of the composition of the spacer, the amount of pressure
applied during the sealing process, and the heat applied during the
sealing process. It is preferred that a plastic spacer deform
slightly when exposed to heat and pressure and then recover some or
all of its original shape when the heat and pressure are removed.
The extent of recovery, or alternatively, the extent to which the
spacer particle is deformed and then resumes some or all or its
original diameter, is known as the recovery factor. The recovery
factor is described in detail in W.O. Patent 9206402, see in
particular FIG. 4 of the cited patent application. In the
measurement of recovery factor a given load is applied to a spacer
particle and the displacement of the spacer caused by the load is
measured (L.sub.1). The load is then removed and the extent to
which the original particle diameter recovers is given as
(L.sub.2). The recovery factor is calculated by (L.sub.2 /L.sub.1).
In view of the variations in display quality, there is a continuing
need for spacer particles that have a balance of properties
affecting control of the cell gap during, and after, the cell
sealing process and impacting both the thermal stability and the
recovery factor of the spacer.
W.O. Pat. Appl. No. 9206402 discloses spheres with certain elastic
modulus and recovery factor properties. The spheres may be applied
as spacers for liquid-crystal display elements. The spheres are
made of polydivinylbenzene, divinylbenzene-styrene copolymer,
divinylbenzene-acrylate copolymers, or polydiallylphthalate.
U.S. Pat. No. 5,231,527 discloses a liquid crystal display with two
sheets of substrates disposed opposite to each other, transparent
electrodes, orientation films, a spacer particle with a certain
range of elastic modulus, and a liquid crystal layer. The spacer
particle may be made of a crosslinked vinyl copolymer.
Despite the teachings of the disclosures, there is a continuing
need to provide improved spacer particles of uniform size which,
and which possess, desirable physical characteristics.
SUMMARY OF THE INVENTION
The present invention provides in one aspect, a composition
comprising a homopolymer or copolymer, comprising as polymerized
units, of multi-functional acrylates and a process for producing a
particle suitable for use as a spacer comprising:
a) forming polymeric pre-seed particles by the emulsion
polymerization of an ethylenically unsaturated monomer;
b) increasing the size of pre-seed particles by emulsion
polymerization to form seed particles that are capable of being
increased in diameter;
c) swelling the seed particles, optionally in the presence
multi-functional monomers, preferably 1,4-butanediol diacrylate
and/or 1,6-hexanediol diacrylate, suitable for use as a spacer.
In a second aspect of the present invention, there is provided a
liquid crystal display containing a spacer particle formed from a
homopolymer or copolymer, comprising of multi-functional monomer
units.
DETAILED DESCRIPTION OF THE INVENTION
The spacers of the present invention are used in liquid display
devices which are known in the art and described in the literature.
Typical liquid crystal display arrangements are described in PCT
92/06402 and U.S. Pat. No. 5,231,527. Liquid crystal display
arrangements of the present invention comprise two sheets of
substrates disposed opposite to each other; with transparent
electrodes disposed on each of said substrates and orientation
films disposed over transparent electrode, the spacer particle of
the present invention and a liquid crystal layer disposed over the
orientation films.
The seed particles of the present invention are increased in size,
i.e., diameter, through the addition of a multi-functional monomer.
As used throughout the specification, multi-functional monomers are
understood to contain two or more polymerizable groups. Suitable
multi-functional monomers may contain two, three, four or more
polymerizable groups. Suitable monomers include tetraethylylene
glycol diacrylate, tripropyleneglycol diacrylate, ethoxylated-bis
phenol-A diacrylate, trimethylolpropane triacrylate,
pentaerythitrol triaacrylate, ethoxylated trimethylolpropane
triacrylate, trivinylcyclohexane and pentaerythritol
tetra-acrylate. Especially preferred are the di-functional acrylate
monomers 1,6-hexanediol diacrylate (HDDA); 1,4-butanediol
diacrylate (BDDA); and mixtures thereof As used throughout this
specification, it is understood that mixtures of the various
monomers are within the scope of the invention.
The final diameter of the spacer particles is preferably from about
1.0 to 15.0 microns, more preferably from 3.0 to 10.0 microns, and
most preferably from about 4.0 to 7.0 microns. The present
invention provides excellent control of the particle size
uniformity; that is, the particles are made with a very narrow
particle-size distribution.
The particle size distribution is such that the standard deviation
of the particle size is typically 5% or less of the mean diameter,
preferably the standard deviation of the particle size is 4% or
less of the mean diameter and most preferably the standard
deviation of the particle size is 3% or less of the mean diameter.
Surprisingly the present invention provides for a standard
deviation that is invariant with particle size diameter, such that
a particle with a diameter of one micron has substantially the same
standard deviation based on diameter as a particle with a diameter
of five microns and additionally a particle with a diameter of ten
microns. Previous disclosures have standard deviations of particle
size that vary with varying particle diameter. Previous disclosures
have standard deviations ranging from 4.5% to 7.0% based upon
particle diameter for diameters ranging from 3.0 microns to 11
microns, respectively.
A further advantage of the present invention is the substantial
elimination of classification processes to produce the narrow
particle size distributions described hereinabove. The narrow
particle size distribution is surprisingly inherent to the process
of making the spacer particles. The removal of aggregates and fines
is minimized, and does not significantly diminish the yield of
spacer particles within the target particle size and having the
desired particle size distribution.
The present invention also provides excellent control of the
particle diameter whereby knowing the number of seed particles, and
controlling precisely the addition of multi-functional monomer, one
can predict the diameter of the spacer particles and control
precisely the diameter of the spacer particles. The diameter can be
controlled to produce spacer particles from about 1.0 to 15.0
microns in diameter and in increments of every 0.1 microns.
A means for controlling particle diameter is provided by the
geometric relationship between volume and diameter and the volume
decrease as a result of converting monomers to a polymer. The
relationship can be expressed as follows:
D.sub.spacer =(D.sub.seed)((Volume increase-1)(Shrinkage
factor)).sup.0.3, wherein:
D.sub.seed is the diameter of the seed particle;
Volume increase=((target diameter of the spacer)/(particle diameter
of the seed)).sup.3 ; and
Shrinkage factor is the volume decrease as a result of converting
monomers to a polymer.
For common monomer/polymer systems, one can obtain shrinkage factor
values from Encyclopedia of Polymer Science and Technology, Vol. 5,
p. 93, 1966. For less common monomer/polymer systems, shrinkage
factors are derived experimentally from the measured volume of the
swollen seed versus the spacer particle or calculated from the
densities of the monomer and resulting polymer Literature values
for typical monomers have shrinkage values which range from 15 to
35. For example, methyl methacrylate has a shrinkage factor of
approximately 21.2, n-butyl methacrylate has a value of 14.3,
styrene has a value 14.5 and acrylonitrile has a value of 31.0.
The particles of the present invention are particularly useful as
spacers due to their narrow particle size distribution and the
physical characteristics these particles possess. The improvements
in properties include enhanced mechanical properties such as
improved compression strength, recovery factors and improved
resistivity. Other improved properties include refractive index and
coefficient of thermal expansion.
The area occupied by a spacer in a liquid crystal display does not
contain any liquid crystal; the liquid crystal layer will be
displaced by the spacer particle. Accordingly, a clear spacer will
scatter some light and appear as a white area. This white area will
increase the brightness of the display in the off-state (when no
light is being transmitted through the display) and thus reduce the
contrast between the on-state and the off-state. One mechanism to
improve the contrast is to use a black, or other darkly colored,
spacer. Therefore, in a preferred embodiment, the spacers of the
present invention are colored. In a most preferred embodiment the
spacers are colored black. Typical methods for coloring the spacer
particles include staining, pigment mixing, and the addition of
dyes to monomers prior to polymerization. Other techniques known in
the art include imbibing colorants into the spacer particles or the
reactive coupling of a colorant and the spacer particle. A
preferred method of coloring the spacer is the reactive coupling of
a colorant to a spacer particle.
In an especially preferred embodiment of the present invention the
spacer particle is provided with adhesive properties. The adhesive
properties aid in keeping the substrates from becoming misaligned
from one another in the manufacturing process and also provide
adhesion between the substrates after the manufacturing process.
The adhesive properties may also reduce the movement of the spacers
on the substrates and thereby reduce the potential for, or the
amount of, damage to the substrates or coatings on the
substrate.
There are known mechanisms for obtaining adhesion between articles:
one is through the use of reactive coupling to create bonds; and
another is through the use of thermoplastic materials known in the
art. Reactive coupling is a process of creating a chemical bond
between two articles through the generation of reactive functional
groups. Reactive functional sites are amenable to chemical bond
formations, including but not limited to free radicals, acidic,
basic, and cationic sites. Methods for generating reactive
functional sites can include UV radiation, thermal activation and
other known processes.
A preferred embodiment of the present invention employs UV
radiation to generate free radicals. It is believed that UV-cure
adhesives adhere two surfaces through the following process: a) a
spacer particle containing adhesive properties is exposed to
ultraviolet radiation such that certain molecules within the
adhesive create free radicals, and b) the free radicals form
covalent bonds with reactive groups contained within the coatings
on the substrate (for example, the alignment layer in a liquid
crystal display) but may also form covalent bonds with reactive
groups contained within the adhesive and also within the spacer
particle in areas not having adhesive properties.
It is believed that thermal-cure adhesives adhere two articles
through a process different from that of UV-cure adhesives. It is
further believed that thermal-cure adhesives adhere articles
through the following process: a) a spacer particle containing an
adhesive layer, whereby the adhesive layer comprises a
thermoplastic resin, is heated generally to a temperature above the
glass transition temperature of the thermoplastic resin contained
within, or substantially comprising, the adhesive layer, and b) the
thermoplastic resin melts or otherwise deforms to form an
attachment to the article, or coatings on the article, through a
mechanism believed to entail intercalation, or pore-filling, of the
thermoplastic adhesive material into pores or irregularities in the
surface of the article or coatings on the article.
In an especially preferred embodiment, reactive coupling,
preferably the generation of free radicals from UV absorption is
employed in combination with a thermoplastic adhesive. An
improvement of using both thermal-cure and UV-cure adhesives is the
curing rate of the adhesive can be accelerated during the assembly
of the liquid crystal display. An additional improvement of using
both thermal-cure and UV-cure adhesives is the added adhesive
strength afforded to the system by multiple points of contacts
between the spacer and the substrates and the multiple mechanisms
for achieving said contact being both thermoplastic and reactive
coupling.
Suitable materials for use as thermoplastics include
poly(meth)acrylate, polyolefins, polyurethanes and the like.
Suitable materials for use in reactive coupling include
aryldiazonium salts, diarylhalonium salts, triarylsulfonium salts,
epoxides, anhydrides, carboxylic acids, hydroxy-containing
compounds, amines, nitrobenzyl esters, sulfones, phosphates,
n-hydroxyimide sulfonates, cobalt-amine and alkyl amine salts,
O-acyloximes and diazonaphthoquinones. A preferred embodiment is
the use of reactive coupling agents which can be incorporated into
a polymer. An especially preferred embodiment is the use of
2-hydroxy-(3-methacryloxy)-propyl-1-(2-benzoyl) benzoate, which is
available from the Rohm and Haas Company.
In a highly preferred embodiment of the present invention, a
mechanism is provided to incorporate a spacer with a thin layer on
the outer-most surface of the spacer (also known as a vicinal
layer) having adhesive properties, containing both reactive
coupling and thermoplastics, such that the vicinal layer is a part
of the spacer and is distinguishable from a coating contacting the
surface of the spacer as previously disclosed in the art. The
vicinal layer includes from 0.1 to 90 weight percent reactive
coupling moieties and from 10 to 99.9 weight percent
thermoplastic.
In another embodiment of the present invention conductive materials
are applied to the surface of the spacer. The conductive material
may be selected from conductive polymers, intrisinically conductive
polymers, doped polymers, and metals. Suitable conductive polymers
include polymers such as polyacrylonitrile butadiene styrene,
polyvinyl chlorides, polyphenylene-based alloys, or polycarbonate
blended with one or more anionic compounds to instill conductivity
such as alkali salts, nonionic compounds such as fatty acid esters
and cationic compounds such as quaternary ammonium salts. Suitable
intrisinically conductive polymers include such as polythiophene,
polypyrrole, poly(phenylenesulfide), poly(phenylenevinylene),
polyacetylene, polyaniline and polyisothianaphthene. Suitable doped
polymers include such as polyacetylene doped with either
I.sub.3.sup.- or Na.sup.+ ; polypyrrole doped with BF.sub.4.sup.-
or ClO.sub.4.sup.- ; polythiophene doped with BF.sub.4.sup.-,
ClO.sub.4.sup.-, or FeCl.sub.4 ; polyazulene doped with
BF.sub.4.sup.- or ClO.sub.4.sup.- ; and polythienylenevinylene
doped with AsF.sub.5. Suitable metals include highly conductive
species such as but not limited to copper, nickel, aluminum, gold
and the like. Especially preferred is gold. Suitable methods for
coating spacer particles with conductive materials are set forth at
length in WO 9206402.
The particles which are used as spacers are prepared in a
multi-step process which includes: 1) the emulsion polymerization
of a pre-seed particle, which is preferably mildly crosslinked; 2)
emulsion polymerization of pre-seed particles to form seed
particles; 3) swelling of the seed particles with monomer and
polymerizing said monomers to form highly-crosslinked spacer
particles; and 4) the optional incorporation of adhesive
properties, conductive coatings or colorants to the spacer
particles.
To prepare spacer particles of the present invention, an aqueous
emulsion of multi-functional monomers is combined with an aqueous
emulsion of seed particles. Preferably, the combined emulsions are
mechanically agitated at a rate sufficient to cause intimate mixing
of the two emulsions but not so severe that shear forces cause
coalescence of particles or particle breakdown. The seed particles
are swelled by the monomer material, forming droplets. Following
this primary swelling, the monomers are polymerized.
The seed particles are prepared in an aqueous emulsion from the
emulsion polymerization of one or more ethylenically unsaturated
monomers. Emulsion polymerization techniques are known to those
skilled in the art. For example, emulsion polymerization techniques
are discussed in U.S. Pat. Nos. 3,037,952 and 2,790,736. Emulsion
polymerization techniques are also discussed in Emulsion
Polymerisation Theory and Practice, D. C. Blackley, Applied Science
Publishers Ltd., London (1975). In emulsion polymerization methods,
a surfactant is typically used, and the size of seed particles
formed is partly determined by the amount and type of surfactant.
For purposes of the present invention, it is desirable to form seed
particles of a size range from 0.1 to 1.0 microns in diameter,
preferably from 0.3 to 0.8 and most preferably from 0.4 to 0.7
microns in diameter (Wu et al., U.S. Pat. No. 5,237,004; see, for
example, Examples 1, 5, and 6). The particle size desired for the
seed particles is determined by the target particle size for the
spacer particles. Particles of a useful size range may be prepared
with surfactant concentrations of from about 0.1 weight percent to
about 5 weight percent, based on the total weight of monomers,
depending on the type of surfactant used. When non-ionic
surfactants are used, it may be preferred to use up to about 10
weight percent surfactant.
Common surfactants are well known to those skilled in the art, and
may be found in, for example, Porter, M. R., Handbook of
Surfactants, Chapman and Hall, New York, 1991. Examples of useful
surfactants for the present invention include ionic surfactants
such as, for example, sodium lauryl sulfate, dioctylsulfosuccinate,
sodium polyoxyethylene lauryl ether sulfate, sodium dodecyl
benzenesulfonate; and non-ionic surfactants such as, for example,
glycerol aliphatic esters, polyoxyethylene aliphatic esters,
polyoxyethylene alcohol ethers; and stearic acid monoglyceride.
Preferably anionic surfactants are employed, such as for example,
alkyl, aryl or alkanyl sulfates, sulfonates, phosphates or
succinates and their ethoxylated derivatives, non-ionic surfactants
and the like. Most preferably dodecylbenzone sulfonate is employed
as a stabilizing agent.
Water soluble polymers such as polyvinyl alcohol, polyvinyl
pyrrolidone, carboxyalkyl celluloses and hydroxyalkyl celluloses
may also be incorporated into the polymerization mixture for
additional stabilization of the pre-seed and seed particles.
The seed particles comprise polymer chains. The seed particles are
preferably formed by polymerization in the presence of a pre-seed
emulsion. The pre-seed emulsion is an emulsion of polymeric
particles and is also formed by well-known aqueous emulsion
methods. In order to achieve a high degree of swelling, it is
important that the molecular weight of the seed particle polymer
chains be low. The ability to swell the seed particle increases
with decreasing molecular weight of the polymer comprising the seed
particle. For example, a molecular weight of 200 to 2,000 provides
the ability to swell the seed on a volume basis of from about 200
to 1,000 increase in volume. A higher molecular weight of 5,000 to
100,000 reduces the ability to swell the seed on a volume basis a
factor of from about 5 to 15 increase in volume.
The pre-seed particles are also prepared in an aqueous emulsion
from the emulsion polymerization of one or more ethylenically
unsaturated monomers. In a highly preferred embodiment of the
present invention the monomers used to form the pre-seed are
selected from the group consisting of butyl acrylate, butylene
glycol diacrylate, and allyl methacrylate. In a preferred
embodiment, the seed particle is comprised of from 10 to 90 percent
by weight butyl acrylate, from 5 to 45 percent by weight styrene,
and from 5 to 45 percent by weight hexanethiol and in a most
preferred embodiment, the seed particle is comprised of from 50 to
80 percent by weight butyl acrylate, from 10 to 25 percent by
weight styrene, and from 10 to 25 percent by weight
hexanethiol.
Emulsion polymerization processes of the present invention produces
pre-seed particles with narrow particle size distributions, having
a mean diameter within the range of from 0.05 to about 0.5 micron
diameter, most preferably having a diameter of from 0.15 to 0.4
micron diameter. In a preferred embodiment, the pre-seed particle
is comprised of from 40 to 100 percent by weight butyl acrylate,
from 0 to 30 percent by weight butylene glycol diacrylate, and from
0 to 30 percent by weight allyl methacrylate. In a most preferred
embodiment, the pre-seed particles are comprised of from 80 to 100
percent butyl acrylate, from 0 to 10 percent by weight butylene
glycol diacrylate, and from 0 to 10 percent by weight allyl
methacrylate.
The pre-seed polymer may be crosslinked. As is well known to those
skilled in the art, crosslinking may be achieved by the use of
polyethylenically unsaturated monomers. Examples of
polyethylenically unsaturated monomers useful as crosslinkers for
forming the pre-seed emulsion include allyl methacrylate (ALMA);
dicyclopentenyl acrylate and methacrylate; glycidyl methacrylate;
glycidyl acrylate; acrylate and methacrylate esters of neopentyl
glycol monodicyclopentenyl ether, epoxy-containing acrylates and
methacrylates; divinylbenzene and dicyclopentenyloxyethyl acrylate
and methacrylate.
Ethylenically unsaturated monomers useful in forming the pre-seed
particles include vinyl aromatic monomers such as styrene,
.alpha.-methylstyrene, vinyltoluene, vinylanthracene;
ethylvinylbenzene and vinylnaphthalene. Non-aromatic vinyl
monomers, such as vinyl acetate, hydrolyzed vinyl acetate, vinyl
chloride, acrylonitrile, (meth)acrylic acids and alkyl esters or
amides of (meth)acrylic acids (such as methyl acrylate, methyl
methacrylate, ethyl acrylate, butyl methacrylate, methyl
methacrylamide and dimethylaminopropyl methacrylamide), may also be
used in forming the seed particles of the present invention. The
expression (meth)acrylic acid is intended to include methacrylic
acid and acrylic acid; the expression is used similarly in, e.g.,
methyl (meth)acrylate, ethyl (meth)acrylate, and the like. Also
useful are halogenated aromatic monomers, such as, for example,
pentafluorophenyl methacrylate; and halogenated non-aromatic
monomers, such as, for example, haloalky acrylates and
methacrylates. Copolymers, such as those prepared from mixtures of
any of the aforementioned monomers, may also be prepared in forming
the seed particles of the present invention. Especially preferred
are mixtures of butyl acrylate, butylene glycol diacrylate and
alkyl methacrylate.
Chain transfer agents such as, for example, mercaptans,
polymercaptans, and polyhalogen compounds may optionally be added
to the monomers in order to moderate molecular weight. Specific
examples include alkyl mercaptans such as t-dodecyl mercaptans and
hexanethiol; alcohols such as isopropanol, isobutanol, lauryl
alcohol, and t-octyl alcohol; and halogenated compounds such as
carbon tetrachloride, tetrachloroethylene, and trichlorbromoethane.
For forming the seed particles, the amount of chain transfer agent
required may be from about 5 percent to about 20 percent by weight,
although amounts above 20 percent may be required depending on the
molecular weight desired. It is preferred that the polymer chains
have a molecular weight of from about 200 to about 10,000.
The amount of seed in the seed emulsion is determined by the
desired final size of the spacer particles. The emulsion of seed
particles may range up to 50 percent seed particles by weight, and
has no theoretical lower limit.
For forming droplets with narrow particle size distributions
containing multi-functional monomers, an emulsion of the monomers
in water is used. The emulsion of multi-functional monomers may be
from 1 percent to 80 percent monomers by weight, preferably from 50
percent to 70 percent. The emulsion of multi-functional monomers is
combined with the aqueous emulsion of seed particles in either a
batch-wise or a continuous addition process. In the case where the
addition is by a batch process, the order of addition is not
critical. The swelling of the seed with multi-functional acrylic
monomer is accomplished such that the final particle size of the
spacer is typically from 1.1 to about 10 times the diameter of the
initial seed particle. The process of forming uniformly sized
polymer particles useful as spacers in the present invention from
seed polymer particles and water insoluble monomers is thoroughly
described in U.S. Pat. No. 5,147,937. Other techniques for
preparing spherical polymer particles are found in U.S. Pat. No.
5,346,954.
In order to ensure that the multi-functional acrylic monomers will
swell the seed to form a particle, it is preferred that a transport
agent be used. Suitable transport agents include acetone, methanol,
isopropyl alcohol and methylene chloride. The transport agent may
also be a macromolecular organic compound having a hydrophobic
cavity. A macromolecular organic compound having a hydrophobic
cavity is a polymeric molecule, typically cylindrical or
approximately cylindrical, which typically has a hydrophilic
exterior but has a hydrophobic interior. Such a compound may be
used to transport hydrophobic substances in an aqueous
environment.
Macromolecular organic compounds having a hydrophobic cavity,
useful in the method of the present invention, include cyclodextrin
and derivatives thereof, cyclic oligosaccharides having a
hydrophobic cavity, such as cycloinulohexose, cycloinuloheptose,
and cycloinuloctose; calyxarenes; and cavitands.
If a transport agent is used and the transport agent is
macromolecular, cyclodextrin is the preferred macromolecular
organic compound to be used as a transport agent. The selection of
cyclodextrin and derivatives thereof useful in the method of the
present invention is determined by the solubility of the
cyclodextrin and cyclodextrin derivatives in the aqueous medium and
by the solubility of the species formed by the association of the
transport agent and the monomer. Suitable cyclodextrins useful in
the method of the present invention include: .alpha.-cyclodextrin,
.beta.-cyclodextrin, and .gamma.-cyclodextrin. The preferred
cyclodextrin derivative is methyl .beta.-cyclodextrin.
The cyclic oligosaccharides having a hydrophobic cavity, such as
cycloinulohexose, cycloinuloheptose, and cycloinuloctose, are
described by Takai et al in Journal of Organic Chemistry, 59(11),
2967-2975 (1994).
The calyxarenes useful in the method of the present invention are
described in U.S. Pat. No. 4,699,966.
The cavitands useful in the method of the present invention are
described in Italian patent application No. 22522 A/89 and by Moran
et al in Journal of the American Chemical Society, 184, 5826-28
(1982).
The amount of transport agent to be used is partly determined by
the composition of the transport agent. If the transport agent is a
cyclodextrin, the weight ratio of cyclodextrin to monomer may range
from about 1:1000 to about 10:100 and is typically from about 1:100
to about 5:100, more typically about 2:100. The lower limit is
determined by such things as the desired rate of transport.
In a preferred embodiment, the amount of optional cyclodextrin is
from 0 to 20 percent by weight based on the total monomer and
optional cyclodextrin and in a most preferred embodiment the amount
of optional cyclodextrin is from 0.5 to 10 percent by weight based
on the total monomer and optional cyclodextrin.
Initiators useful for emulsion polymerization reactions can be
water or oil soluble. Water soluble, free radical initiators are
preferred for emulsion polymerizations. Initiators used to
polymerize multi-functional monomers in the preparation of the
spacer particle are preferably oil soluble.
The spacer particles formed by the method described herein exhibit
many highly desirable physical characteristics, such as compression
strength, recovery factor, resistivity, thermal expansion and
refractive index.
Compression strength is the amount of force the particle can
withstand before it crushes. The spacers of the present invention
have a compression strength of greater than 150 kilograms per
square millimeter (kg/mm.sup.2). This high compression strength
value is desired to ensure that spacer particles do not fracture or
crush during the cell-sealing process.
The spacers of the present invention provide recovery factors of
greater than 45 percent, preferably greater than 50 percent and
most preferably greater than 53 percent. Recovery factors are
important measurements because during cell sealing processes,
typically, the two opposing substrates are compressed and the
spacers must compress slightly with pressure and re-expand upon
releasing the pressure. The recovery factor can be used to predict
the cell-gap maintained after the cell-assembly process.
The resistivity of the spacers is also greatly improved by the
spacers of the present invention. The spacers have resistivity of
greater than 4.0.times.10.sup.15 ohm-cm, Preferably the resistivity
is greater than 5.0.times.10.sup.15 ohm-cm. High resistivity is
important in a spacer for liquid crystal displays. The liquid
crystal molecules allow the transmission of light through a display
in response to an electric field. Material within the
liquid-crystal layer degrading the dielectric property of the
liquid crystal layer, or alternatively increasing the conductivity
of the liquid crystal layer, will adversely affect display
performance.
The coefficient of thermal expansion of the spacers is also greatly
improved by the spacers of the present invention. The spacers have
coefficients of thermal expansion greater than 100.times.10.sup.-6
/.degree. C. and less than 125.times.10.sup.-6 /.degree. C.
Preferably the coefficient of thermal expansion is greater than
110.times.10.sup.-6 /.degree. C. and less than 120.times.10.sup.-6
/.degree. C. The coefficient of thermal expansion of a spacer will
define, in part, the spacers ability to expand and contract in
response to temperature. Ideally, the coefficient of thermal
expansion of a spacer will match that of the liquid crystal layer
such that when the liquid crystal display is exposed to thermal
cycling the expansion and contraction of the spacer particle will
match the expansion and contraction of the liquid crystal layer.
Sufficient mismatch of the coefficient of thermal expansion between
that of the spacer and that of the liquid crystal layer may result
in the formation of voids upon thermal cycling and adversely affect
display performance.
The index of refractiion of a spacer is ideally matched to that of
the substrate. The index of refraction for a glass substrate used
in a liquid crystal display is in the range of 1.53 to 1.55. The
spacers of the present invention have refractive indices of about
1.50.
The following examples are intended to illustrate various
embodiments of the present invention, such as the process by which
the compositions of this invention are made, the compositions of
this invention, and the unexpected beneficial properties of the
compositions of this invention when applied as spacers in liquid
crystal displays.
EXAMPLE 1
Preparation of Pre-seed
The following mixtures were prepared:
______________________________________ Parts by Mixture Component
Weight.sup..dagger. ______________________________________ A water
180 sodium carbonate 0.40 B butyl acrylate 98.0 butylene glycol
diacrylate 0.25 allyl methacrylate 1.75 22.5% aqueous sodium
dodecylbenzenesulfonate 2.22 water 40.8 C potassium persulfate 0.06
water 11.9 ______________________________________ .sup..dagger. per
100 parts of monomer
A reactor equipped with a stirrer and condenser and blanketed with
nitrogen was charged with Mixture A and heated to 82.degree. C. To
the reactor contents was added 10% of Mixture B and 25% of Mixture
C. The temperature was maintained at 82.degree. C. and the mixture
was stirred for 1 hour, after which the remaining portions of
Mixture B and Mixture C were added to the reactor, with agitation
over a period of 90 minutes. Agitation was continued at 82.degree.
C. for 2 hours, after which the reactor contents were cooled to
room temperature. The particle size of the resulting emulsion
particles was 0.2 micron, as measured by a Brookhaven Instruments
BI-90.
EXAMPLE 2
Preparation of Seed
The particles of Example 1 were grown to 0.5 micron diameter using
an emulsion of butyl acrylate and styrene. The following mixtures
were prepared:
______________________________________ Parts by Mixture Component
Weight.sup..dagger. ______________________________________ D water
185 Sodium carbonate 0.081 Emulsion from Example 1 at 29.6% solids
30.30 E butyl acrylate 82 styrene 18 10% aqueous sodium
dodecylbenzenesulfonate 2.5 water 32 F 1-hexanethiol 18.8 10%
aqueous sodium dodecylbenzenesulfonate 2.8 water 11 G potassium
persulfate 0.11 water 18 H t-Butyl hydroperoxide 70X .RTM. (from
the Lucidol 0.18 Division of Pennwalt Corp.) water 3.7 I 3% aqueous
sodium formaldehyde sulfoxylate 0.41
______________________________________ .sup..dagger. per 100 parts
of monomer
Mixture D was added to a reactor and heated to 88.degree. C. with
agitation. Mixtures E, F, and G were added, with agitation, to the
reactor over a period of 3 hours, after which the temperature was
maintained at 88.degree. C., with agitation, for 90 minutes. The
reactor contents were cooled to 65.degree. C. Mixtures H and I were
added, and the reactor contents were maintained at 65.degree. C.,
for 1 hour, after which the reactor contents were cooled to room
temperature. The resulting emulsion polymer particles had a
diameter of 0.5 micron as measured by a Brookhaven Instruments
BI-90.
EXAMPLE 3
Preparation of 4.90-micron pBDDA Particles
The particles of Example 2 werre grown to 4.9 micron diameter using
an emulsion of 1,4-butanediol diacrylate. The following mixtures
were prepared:
______________________________________ Parts by Mixture Component
Weight.sup..dagger. ______________________________________ J water
210 3% aqueous Solusol .RTM. (available from American 1.52
Cyanamid, Fine Chemical Div.) K 1,4-butanediol diacrylate 100 50.8%
aqueous methyl beta-cyclodextran 1.78 75% aqueous Solusol .RTM.
0.81 water 89 L Emulsion from Example 2 at 7.76% solids 1.4275
water 12.5 M tert-Butyl peroctoate 0.80 3% aqueous Solusol .RTM.
3.33 0.11% aqueous sodium p-nitrosophenolate 1.50 10% aqueous
poly(n-vinylpyrrolidone) 50 water 17.5
______________________________________ .sup..dagger. per 100 parts
of monomer
Mixture J was added into a reactor and heated to 65.degree. C. with
agitation. Mixture K was blended in a Waring blender for 5 minutes
to form an emulsion. Mixture L, and the blended emulsion K were
charged into the reactor. The reactor was stirred at 60.degree. C.
for 2 hours and cooled to 25.degree. C. Mixture M was blended in a
Waring blender for 3 minutes to form an emulsion. This emulsion was
added to the reactor. After 1 hour agitation at 25.degree. C., the
reactor was heated to 60.degree. C. and held for 1 hour at
60.degree. C. before heating to 70.degree. C. Agitation was
continued at 70.degree. C. for 1.5 hours, after which the reactor
contents were cooled to room temperature. The polymer particles
from the reaction mixture, when examined by an optical microscope,
were uniformly sized. When analyzed by a Coulter Corporation
Multisizer IIE particle size analyzer, the particles had a mean
diameter of 4.90 microns and a standard deviation is 0.19
micron.
The compositions of this invention were tested for compression
strength, and recovery factor. A commercial spacer sample,
Micropearl SP-205 from Sekisui Fine Chemical, was tested as a
comparative example in each test. Results of the tests are given in
Table 1.
TABLE 1 ______________________________________ SP-205 pHDDA pBDDA
______________________________________ Compression Strength
(kg/mm.sup.2) 137 172 234 Recovery Factor (%) 44 53 47
______________________________________ p HDDA = poly(1,6hexanediol
diacrylate) p BDDA = poly(1,4butanediol diacrylate)
The above results demonstrate the compositions of this invention
have surprisingly improved compression strength and recovery
factors compared with the spacer from the cited disclosure.
EXAMPLE 4
Preparation of 1.48-micron pBDDA Particles
In this example the particles in the emulsion of Example 2 are
grown to 1.48 micron diameter using an emulsion of 1,4-butanediol
diacrylate. The following mixtures were prepared:
______________________________________ Parts by Mixture Component
Weight.sup..dagger. ______________________________________ N water
210 3% aqueous Solusol .RTM. 1.52 O 1,4-butanediol diacrylate 100
50.8% aqueous methyl beta-cyclodextran 1.78 75% aqueous Solusol
.RTM. 0.81 water 89 P Emulsion from Example 2 at 30.44% solids
16.31 water 12.5 Q tert-Butyl peroctoate 0.80 3% aqueous Solusol
.RTM. 3.33 0.11% aqueous sodium p-nitrosophenolate 1.50 10% aqueous
poly(n-vinylpyrrolidone) 50 water 17.5
______________________________________ .sup..dagger. per 100 parts
of monomer
Mixture N was added into a reactor and heated to 65.degree. C. with
agitation. Mixture M was blended in a Waring blender for 5 minutes
to form an emulsion. Mixture P, and the blended emulsion 0 were
charged into the reactor. The reactor was stirred at 60.degree. C.
for 2 hours and cooled to 25.degree. C. Mixture Q was blended in a
Waring blender for 3 minutes to form an emulsion. This emulsion was
added to the reactor. After 1 hour agitation at 25.degree. C., the
reactor was heated to 60.degree. C. and held for 1 hour at
60.degree. C. before heating to 70.degree. C. Agitation was
continued at 70.degree. C. for 1.5 hours, after which the reactor
contents were cooled to room temperature. The polymer particles
from the reaction mixture, when examined by an optical microscope,
were uniformly sized. Analyzed by a particle size analyzer, Coulter
Corporation Multisizer IIE, the particles have a mean diameter of
1.48 microns and the standard deviation is 0.05 micron.
EXAMPLE 5
Preparation of 1.52-micron pBDDA Particles
The particles in the emulsion of Example 2 are grown to 1.52 micron
diameter using an emulsion of 1,4-butanediol diacrylate. The
following mixtures were prepared:
______________________________________ Mixture Component Parts by
Weight.sup..dagger. ______________________________________ R water
210 3% aqueous Solusol .RTM. 1.52 S 1,4-butanediol diacrylate 100
50.8% aqueous methyl beta-cyclodextran 1.78 75% aqueous Solusol
.RTM. 0.81 water 89 T Emulsion from Example 2 at 30.44% solids
13.36 water 12.5 U tert-Butyl peroctoate 0.80 3% aqueous Solusol
.RTM. 3.33 0.11% aqueous sodium p-nitrosophenolate 1.50 10% aqueous
poly(n-vinylpyrrolidone) 50 water 17.5
______________________________________ .sup..dagger. per 100 parts
of monomer
Mixture R was added into a reactor and heated to 65.degree. C. with
agitation. Mixture S was blended in a Waring blender for 5 minutes
to form an emulsion. Mixture T, and the blended emulsion S were
charged into the reactor. The reactor was stirred at 60.degree. C.
for 2 hours and cooled to 25.degree. C. Mixture U was blended in a
Waring blender for 3 minutes to form an emulsion. This emulsion was
added to the reactor. After 1 hour agitation at 25.degree. C., the
reactor was heated to 60.degree. C. and held for 1 hour at
60.degree. C. before heating to 70.degree. C. Agitation was
continued at 70.degree. C. for 1.5 hours, after which the reactor
contents were cooled to room temperature. The polymer particles
from the reaction mixture, when examined by an optical microscope,
were uniformly sized. Analyzed by a particle size analyzer, Coulter
Corporation Multisizer IIE, the particles have a mean diameter of
1.52 microns and the standard deviation is 0.05 micron.
EXAMPLE 6
Incorporation of Adhesive Property onto 4.90-micron pBDDA
Particle
Adhesive chracteristics are incorporated onto the particles in the
emulsion of Example 3. The following mixtures were prepared:
______________________________________ Parts by Mixture Component
Weight.sup..dagger. ______________________________________ V
Emulsion from Example 3 at 21.74% solids 5000 water 139 W 3%
aqueous Solusol .RTM. 2.28 Sodium formaldehyde sulfoxylate 0.07
water 1276 X 2-hydroxy-(3-methacryloxy)-propyl-1-(2- 8.33
benzoyl)benzoate (Rohm and Haas Company) tert-Butyl methacrylate
91.67 Y tert-Butyl hydroperoxide 70X .RTM. (from Lucidol 0.15
Division of Pennwalt Corp.) 3% aqueous Solusol .RTM. 5.07 water 634
______________________________________ .sup..dagger. per 100 parts
of monomer
Mixture V was added into a reactor and heated to 75.degree. C. with
agitation. One half of Mixture W was then charged into the reactor.
The second half of Mixture W, and Mixtures X and Y were added into
the reactor in 3 hours. Agitation was continued at 75.degree. C.
for 1 hours, after which the reactor contents were cooled to room
temperature. The polymer particles from the reaction mixture, when
examined by an optical microscope, remained uniformly sized. The
incorporation of the
2-hydroxy-(3-methacryloxy)-propyl-1-(2-benzoyl)benzoate and
tert-butyl methacrylate monomers imparted an adhesive property to
the particles.
EXAMPLE 7
Preparation of 4.47-micron pBDDA Particles
The particles in the emulsion of Example 2 are grown to 4.47 micron
diameter using an emulsion of 1,4-butanediol diacrylate. The
following mixtures were prepared:
______________________________________ Mixture Component Parts by
Weight.sup..dagger. ______________________________________ A water
210 3% aqueous Solusol .RTM. 1.52 B 1,4-butanediol diacrylate 100
50.8% aqueous methyl beta-cyclodextran 178 75% aqueous Solusol
.RTM. 0.81 water 89 C Emulsion from Example 2 at 7.76% solids
1.7636 water 12.5 D tert-Butyl peroctoate 0.80 3% aqueous Solusol
.RTM. 3.33 0.11% aqueous sodium p-nitrosophenolate 1.50 10% aqueous
poly(n-vinylpyrrolidone) 50 water 17.5
______________________________________ .sup..dagger. per 100 parts
of monomer
Mixture A was added into a reactor and heated to 65.degree. C. with
agitation. Mixture B was blended in a Waring blender for 5 minutes
to form an emulsion. Mixture C, and the blended emulsion B were
charged into the reactor. The reactor was stirred at 60.degree. C.
for 2 hours and cooled to 25.degree. C. Mixture D was blended in a
Waring blender for 3 minutes to form an emulsion. This emulsion was
added to the reactor. After 1 hour agitation at 25.degree. C., the
reactor was heated to 60.degree. C. and held for 1 hour at
60.degree. C. before heating to 70.degree. C. Agitation was
continued at 70.degree. C. for 1.5 hours, after which the reactor
contents were cooled to room temperature. The polymer particles
from the reaction mixture, when examined by an optical microscope,
were uniformly sized. Analyzed by a particle size analyzer, Coulter
Corporation Multisizer IIE, the particles have a mean diameter of
4.47 microns and the standard deviation is 0.14 micron.
EXAMPLE 8
Preparation of 4.58-micron pBDDA Particles
The particles in the emulsion of Example 2 are grown to 4.58 micron
diameter using an emulsion of 1,4-butanediol diacrylate. The
following mixtures were prepared:
______________________________________ Mixture Component Parts by
Weight.sup..dagger. ______________________________________ A water
210 3% aqueous Solusol .RTM. 1.52 B 1,4-butanediol diacrylate 100
50.8% aqueous methyl beta-cyclodextran 1.78 75% aqueous Solusol
0.81 water 89 C Emulsion from Example 2 at 7.76% solids 1.6462
water 12.5 D tert-Butyl peroctoate 0.80 3% aqueous Solusol .RTM.
3.33 0.11% aqueous sodium p-nitrosophenolate 1.50 10% aqueous
poly(n-vinylpyrrolidone) 50 water 17.5
______________________________________ .sup..dagger. per 100 parts
of monomer
Mixture A was added into a reactor and heated to 65.degree. C. with
agitation. Mixture M was blended in a Waring blender for 5 minutes
to form an emulsion. Mixture C, and the blended emulsion B were
charged into the reactor. The reactor was stirred at 60.degree. C.
for 2 hours and cooled to 25.degree. C. Mixture D was blended in a
Waring blender for 3 minutes to form an emulsion. This emulsion was
added to the reactor. After 1 hour agitation at 25.degree. C., the
reactor was heated to 60.degree. C. and held for 1 hour at
60.degree. C. before heating to 70.degree. C. Agitation was
continued at 70.degree. C. for 1.5 hours, after which the reactor
contents were cooled to room temperature. The polymer particles
from the reaction mixture, when examined by an optical microscope,
were uniformly sized. Analyzed by a particle size analyzer, Coulter
Corporation Multisizer IIE, the particles have a mean diameter of
4.58 microns and the standard deviation is 0.16 micron.
EXAMPLE 9
Preparation of 1.99-micron pBDDA Particles
In this example the particles in the emulsion of Example 2 are
grown to 1.99 micron diameter using an emulsion of 1,4-butanediol
diacrylate. The following mixtures were prepared:
______________________________________ Mixture Component Parts by
Weight.sup..dagger. ______________________________________ A water
210 3% aqueous Solusol .RTM. 1.52 B 1,4-butanediol diacrylate 100
50.8% aqueous methyl beta-cyclodextran 1.78 75% aqueous Solusol
.RTM. 0.81 water 89 C Emulsion from Example 2 at 30.49% solids
5.6681 water 12.5 D tert-Butyl peroctoate 0.80 3% aqueous Solusol
.RTM. 3.33 0.11% aqueous sodium p-nitrosophenolate 1.50 10% aqueous
poly(n-vinylpyrrolidone) 50 water 17.5
______________________________________ .sup..dagger. per 100 parts
of monomer
Mixture A was added into a reactor and heated to 65.degree. C. with
agitation. Mixture M was blended in a Waring blender for 5 minutes
to form an emulsion. Mixture C, and the blended emulsion B were
charged into the reactor. The reactor was stirred at 60.degree. C.
for 2 hours and cooled to 25.degree. C. Mixture D was blended in a
Waring blender for 3 minutes to form an emulsion. This emulsion was
added to the reactor. After 1 hour agitation at 25.degree. C., the
reactor was heated to 60.degree. C. and held for 1 hour at
60.degree. C. before heating to 70.degree. C. Agitation was
continued at 70.degree. C. for 1.5 hours, after which the reactor
contents were cooled to room temperature. The polymer particles
from the reaction mixture, when examined by an optical microscope,
were uniformly sized. Analyzed by a particle size analyzer, Coulter
Corporation Multisizer IIE, the particles have a mean diameter of
1.99 microns and the standard deviation is 0.07 micron.
EXAMPLE 10
Preparation of 2.11-micron PBDDA Particles
The particles in the emulsion of Example 2 are grown to 2.11 micron
diameter using an emulsion of 1,4-butanediol diacrylate. The
following mixtures were prepared:
______________________________________ Parts by Mixture Component
Weight.sup..dagger. ______________________________________ A water
210 3% aqueous Solusol .RTM. (available from American 1.52 Cyanamid
Fine Chemical Div.) B 1,4-butanediol diacrylate 100 50.8% aqueous
methyl beta-cyclodextran 1.78 75% aqueous Solusol .RTM. 0.81 water
89 C Emulsion from Example 2 at 30.49% solids 4.8757 water 12.5 D
tert-Butyl peroctoate 0.80 3% aqueous Solusol .RTM. 3.33 0.11%
aqueous sodium p-nitrosophenolate 1.50 10% aqueous
poly(n-vinylpyrrolidone) 50 water 17.5
______________________________________ .sup..dagger. per 100 parts
of monomer
Mixture A was added into a reactor and heated to 65.degree. C. with
agitation. Mixture M was blended in a Waring blender for 5 minutes
to form an emulsion. Mixture C, and the blended emulsion B were
charged into the reactor. The reactor was stirred at 60.degree. C.
for 2 hours and cooled to 25.degree. C. Mixture D was blended in a
Waring blender for 3 minutes to form an emulsion. This emulsion was
added to the reactor. After 1 hour agitation at 25.degree. C., the
reactor was heated to 60.degree. C. and held for 1 hour at
60.degree. C. before heating to 70.degree. C. Agitation was
continued at 70.degree. C. for 1.5 hours, after which the reactor
contents were cooled to room temperature. The polymer particles
from the reaction mixture, when examined by an optical microscope,
were uniformly sized. Analyzed by a particle size analyzer, Coulter
Corporation Multisizer IIE, the particles have a mean diameter of
2.11 microns and the standard deviation is 0.10 micron.
EXAMPLE 11
Application of Conductive Coating on a Particle
A 50 ml beaker was charged with 1.00 gram of spacer particles of
the present invention with a mean particle size of 5.1 micrometers.
30 ml of Conditioner PM-922 (Shipley Company) was heated to
49.degree. C. and charged into the beaker. The suspension was
stirred intermittently with a glass stir rod and the beaker was
placed on a hot plate to maintain the temperature. After 5 minutes
the particles were isolated by filtration from the solution using
a.0.45 micron filter disk (Micron Separation Inc.). The particles
were rinsed 3 times with 20 ml portions of de-ionized water. The
particles were then charged into a 50 ml beaker along with 30 ml of
Neutralizer PM-954 from a heated reservoir maintained at 32.degree.
C. The suspension was placed on a hot plate to maintain the
temperature and stirred intermittently for 5 minutes. The particles
were then collected and washed 3 times with 20 ml portions of
de-ionized water. The particles were then charged into a 50 ml
beaker along with 30 ml of Cataposit 44.RTM. (Shipley Co.) heated
to 32.degree. C. The suspension was placed on a hot plate to
maintain the temperature and stirred intermittently for 4 minutes.
The particles were collected and washed 3 times with 20 ml portions
of de-ionized water. The polymer particles were charged into a 50
ml beaker again and then 30 ml of Accelerator 19 (Shipley Co.)
heated to 32.degree. C. was added. The suspension was placed on a
hot plate to maintain the temperature and stirred intermittently
for 3 minutes. Then the sample was collected by filtration and
washed three times with 20 ml aliquots of de-ionized water. The
sample was again charged into a 50 ml beaker and then 30 ml of
Niposit.RTM. Electroless Nickel PM-980 (Shipley Co.) was added and
heated to 27.degree. C. The suspension was stirred for 3 minutes
and the beaker was placed on a hot plate to maintain the
temperature. Upon addition of the Electroless Nickel solution a
reaction occurred and the polymer particles turned from white to
gray. The polymer particles were isolated and washed an additional
three times with de-ionized water to completely remove any
un-reacted nickel salts or reducing agent. The samples were then
dried in an oven at 40.degree. C. Obtained 0.92 g of a gray
powder.
Under an optical microscope a metallic, mirror-like coating on the
particles could be observed. The samples was analyzed by energy
disperse x-ray using a PGT analyzer on an Electroscan environmental
scanning electron microscope. Nickel could be detected on the
coated particles, but not on the starting polymer particles.
EXAMPLE 12
Physical Testing Results
Spacer particles made with HDDA and BDDA were compared to a
commercially available spacer sold by Sekisui Fire Chemicals,
Micropearl SP-205. The physical property test results were as
follows:
__________________________________________________________________________
Property pBDDA pHDDA SP-205.sup..dagger. Sample Remarks
__________________________________________________________________________
Compression Strength, kg/mm.sup.2 234 172 137 spacer measured @
25.degree. C. Compressive Strength, kpsi 16 13 16.sup..dagger.
block ASTM D695, JIS K7208.sup..dagger. Thermal Expansion Coef.,
10.sup.-6 /.degree.C. 110 120 98.sup..dagger. sheet avg.; from
20-80.degree. C. Recovery Factor (%) 47 53 44 spacer Decomposition
Temp., .degree.C., 267 256 327.sup..dagger. spacer TGA, 1% weight
loss In Air (in Nitrogen) (346) (366) in air & nitrogen Volume
Resistivity, 10.sup.15 Ohm cm 5.3 4.2 0.36.sup..dagger. sheet ASTM
D257 Dielectric Constant, @ 1 kHz 1.6 1.7 2.9.sup..dagger. sheet
ASTM D150 Transmittance 92% 92% 86%.sup..dagger. sheet Haze 2.6%
1.2% 3.5%.sup..dagger. sheet Refractive Index 1.51 1.50
1.57.sup..dagger. sheet Volatile Component 0.02% 0.04% 0.03% spacer
105.degree. C. for 1 hour Chemical Resistance sheet % weight change
after Water 0.7% 0.3% 0.5%.sup..dagger. immersion for 10 days 0.1N
NaOH 0.7% 0.3% -0.2%.sup..dagger. at 20.degree. C. 0.1N HCl 0.7%
0.3% 0.4%.sup..dagger. Acetone 1.0% 2.2% 1.0%.sup..dagger. Toluene
0.4% 1.2% --
__________________________________________________________________________
.sup..dagger. From Sekisui Fine Chemical's product literature for
Micropearl, SP grade
* * * * *